Change-speed gear



Sept. 5; 1944.

R. CHILTON CHANGE SPEED GEAR Filed Ma'rch 20, 1941 INVEN-roR Roland Chi/fan.

III I l mm .h

ATTDRNEY velement by the operator.

PatentedSept. 5, 1944 onANGiz-SPEED GEAR.

Roland Chilton, Ridgewood, N. J., assignor to "Wright Aeronautical Corporation, a corporation of New York Application March 20. 1941,'Serial No..384=,329A

` 2 claims. '(01. 19a-o1) This invention relates to gear shift means for obtaining twoor more different ratios between a driving and a driven shaft. The invention is intended to be of general application although the embodiment shown is taken from designs for a two-speed propeller drive for an aeronautical engine, with certain simplications t eliminate structure not' pertinent to the present invention per se. y

A prime object of the invention is to eliminate the need for friction clutches which, for the powers used in aircraft engines, add excessively to the bulk and weight of the gear and are subject to the-followingv disadvantages: The friction coeiiicients developed in practice vary over 'a wide range while the capacity of the clutch must be in excess of the maximum torque to be transmitted at the minimum coemcient which may be experienced in service. In theslipping period, during each clutch engagement, the torque imwhlchlmay be rigid `with the crankshaft of an posed on the gear-system is that required to slip the clutch as it relatively accelerates the driving and drivenengine and propeller masses to' the new speed relation. Accordingly, the gears must be 'designed to .withstand the maximum torque ever developed by the clutch .whereas the minimum clutch torque must itself be in. excess ofthe maximum power torque to be transmitted.

A further object is to utilize a shiitable dog clutch between driving and driven members and to provide means whereby engagement is permitted only when the clutch members are rotating at substantially the same speed. A meshing device of the character herein disclosed may be called an inhibiting or a balking device winch serves in effect, to preventl clutch engagement under all speed and torque relationships between driving and driven members except when said relationships meet preselected conditions. Stili another object is to provide control devices for an engine which are coordinated with the speed changing clutch. More specically, a feature of the invention resides in novel means for connecting a shifting mechanism with means to ldecelerate and accelerate an engine during shifting so as to insure that the :law clutch elements are brought to the Aunitary speed relationship to which the clutch inhibiting device is` responsive to allow of clutch shift, An associated object is to perform these A functions automatically in response to the movement of a single control Other objects `of theinvention become apparent in reading .the annexeddescription in f connection with the drawing, in which;

Fig. 1 is a. fragmentary longitudinal section through a transmission mechanism; and Fig. 2 is a developed plan of a portion of the mechanism.

Although Fig. 1 depicts a two-speed gearsetin which one ratio is secured through a roller-clutch and another ratio through a jaw clutch, both drive ratios, and in fact additional drive ratios, may be secured by the use of additional gearing and/or additional jaw clutches, the jaw clutches each having the inhibiting mechanism of the invention. As shown, I0 represents a driving shaft engine, this shaft being integral with an inner cam member I2 of a conventional one-way clutch comprising 'rollers I4 embraced by a driven ringA I6, the latter having external gear teeth I8- meshed with a pinion 20 `of a layshaft 22 which in turn is provided with a drive pinion 24 meshed with a driven gear 26 on a, driven shaft 28. The layshaft may be one of several similar circumferentially disposed layshafts each having pinions 22 and 24 and each having in addition, a pinion 29 meshed with a gear 30 secured to a hub 32 piloted at 33 on the driven shaft 28. The gear 30 is axially movable but remains meshed with the pinion 29 at all times, said gear 30 including clutch teeth 34 movable intoand out of, engagement with, clutch teeth 36 rigid with the member I0. A spring 38, reacting on the hub of the gear 26. presses the hub 32 to the right to enforce engagement of the clutch teeth 34 and 36, and this rightward pressure is offset by pistons 40 engaging cylinders 42 rigid with a housing member 44, the pistons 40 acting on a thrust annulus 46 bearing'at 41 on the gear 30. Ratio changes in the gearset are effected by admitting fluid to or withdrawing iluid from thecylinders V n 52 is operated by a manual control rod 58 by which ratio changes arepreselected.

From the abo'veA it will be apparent thatl the low ratiodrive las shown, is accomplished from theshaft I0 through *the'roller clutch I2, I4,

I6, through the gear engagement I8, 20, the

layshaft 22, the gear engagement 24, 26 to the driven shaft 28. During the low ratio drive the gear 30, though meshed with the pinion 29, idles on thedriven shaft 28.`

When the high ratio d rive isy selected, pressure fluid inthe cylinders 42; is released, causing the spring 38 to urge engagement of the clutch teeth system of this kind would be replaced with a friction plate clutch since it is obvious that the clutch teeth 34 and 36 cannot be engaged unless they are rotating, at nearly identical speeds. Part of the essence of this invention consists in providing means to permit engagement of clutch teeth such as 34 and 36 only when they are synchronized so that theymay be engaged or disengaged without catastrophic effect either upon themselves or' upon the rest of the mechanism. vTo this end, I .provide an annulus 66 secured to the shaft I which carries one or more axially extending lingers 62 each engaging a notch 64 in a ring 66 rigid with a cone clutch element 66 which at times is engaged by acomplein'entary cone clutch element 10 formed in the hub of the gear 30. Centrally of the notch 64' is a/deeper notch 12 into which the finger 62 may at times pass, as will bedescribed. The element 66 with its cone clutch element 66 is constrained to axial movement with and with respect to the gear 36 by means of a lock ring 14 and obviously, the ring 66 may rotate with 4 and to a limited degree with respect to the ring 60 dueto the engagement ofthe finger 62 in the relatively wide notch 64.

. Now, assuming that the transmission is in low ratio with the clutch teeth 34 and 36 disengaged,

relief of oil pressure from the cylinders 42 will allow the spring 36 to press the gear 3ll'and its hub 32 toward the right. This will enforce ensagement of the cone clutch 66, 16 andwill press the ring 66 firmly against the finger -`62 ofthe ring 66,` there being slippage in the clutch 66, 1 6 while the driving member I0 and the gear 30 are not at synchronous speed. .Now, if the driving member III be decelerated to the point where it passes synchronism with the member 30, which will continue to rotate due to inertia of the driven load, the ring 66 will, dueto clutch torque. move angularly with respect to the ring 66 a suilicient amount for the finger 62 to drop into the notch 12 thus permitting axial movement to the right of the gear hub k32 with coincidental engagement of the clutch teeth 34, 36 whereupon the other ratio of vdrive is established. Upon acceleration of the driving member` I0, the driving torque is transmitted through the teeth 34, 36 to' afford the will overrun on the clutch rollers I4 with vrespect to the driving member I6.

To return to the low ratio drive, pressure fluid isadmitted to the cylinders 42 and the pistons will urge the gear 30 to the. left to urge disengagement of the clutch teeth 34, 36 but the force exerted by the pistons 46 will be of a sumciently low order that, although greater than the force exerted by the spring 36, vitwill be insuillcient to disengage the'clutch teeth 34, 36 unless drive torque be diminished by decelerating the drive shaft I6 or accelerating the driven shaft 26. If

`the clutch were forcibly disengaged under full torque conditions, the corners of the clutch teeth 34, 36 would be torn oil'.

When this system is applied to the propeller drive gear of an internal combustiony engine, the deceleration a'nd acceleration of the drive shaft vI6 may be coordinated with the gear shift se- 1i oeleration of such large masses would require Y lection by means shown in the lefthand side of` Fig. 1. Thereat, 66 represents the main induction pipe to the engine lin which is-disposed a throttle valve 62 mounted on a shaft 64 which 6 carries a gear 66 meshed with a rack 66 which forms a leftward continuation of a piston rod 66 carrying a piston 62 slidable in a cylinder 64 connected at its righthand end to a pipe 66 having a restricted oriiice 68- at the valve 62. The

piston 32 is urged to the right in its cylinder 64 by a spring N6, and the lefthand end of the cyiinderis vented as at |02 to allow of free action l of the piston.

The piston stroke will be so chosen as to swing l5 the throttle valve 62 through 180 from full open position through closed position to full open position. Now, when the valve control rod 66 is inv the position shown in full lines, the transmission is set for low ratio drive through the roller clutch I4. When a shift is made to high ratio,

the. valve rod 66 is moved to the left as shown in dotted lines, which will relieve fluid pressure from the transmission control cylinders 42 to prepare the clutch 34, 36 for engagement and 25, coincidentally, uid pressure from the pressure supply 64 is directed to the cylinder 94 by which the throttle valve 62'is caused to move from full open, through closed and to full open position, thereby` temporarily decelerating the engine through the synchronization point to permit of the engagement ofthe high speed drive clutch 64, 36. Return of the throttle valve to the full open position affords prompt restoration of full power operation. The oriiice 38 in the throttle control line serves to establish a definite interval of operation of the throttle valve 62 to make sure that the drive shaft I0 decelerates a suiiicient amountl lso that its speed is reduced at least to [that ofthe speed of the gear 30 so that engage- Av4 ment of the clutch teeth 34, 36 is assured.` Although return to the lowl speed ratio is also ac,

companied by temporary closure of the engine throttle, the time interval for this transition is not material so long as a reversal of torque takes place between the drive member I0 and the driven obviously feasible to' utilize any other control means by which speed change is afforded between the driving and driven members.

In all gear-shift systems it is necessary tovv bring the transmission to zero torque to effect a shift. In conventional automobile transmissions, high ratio drive, and in this drive the gear I6 m) :matically closing a throttle which is immediately opened again.

Applicant is aware that, in conventional automobile transmissions, friction "synchro-mesh de- .vices are used to coerce the members to be ens gaged to unitary speed. When the main frictionA clutch which disconnects the transmission from the engine has little drag and small flywheel effect, the required friction capacity in this coercive type of synchronizer is relatively small. However, in the current invention, where such main friction clutch is eliminated and where the systems to be synchronized comprise large iiywheel masses as in airplane engines and propel-v lers, a'synchronizing device to effect relative de extremely great frictional capacity. It is therefore important to note that, in the device of this invention, the friction clutch El of the inhibitor merely has to move the light inhibitor member gine itself, under automatic throttle manipulation as described. The inhibitor is a novel device to insure that the automatic meshing action shall occur only at that instant during this acceleration and deceleration at which the parts reach unitary speed, i. e., the instant of transition at which the relative speed changes from positive to negative (or viceversa) and'at which, accordingly, the friction torque from the inhibitor clutch 88 reverses and the inhibitor finger 82 is moved from whichever shoulder 84 it may previously have engaged so as to fall into the slot 12.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to Athose skilled in the art, after'understanding my invention, that various changes and modications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modications and changes.

I claim as my invention:

1. In combination, an internal combustion engine, a change speed gearset therefor including a pair of engageable toothed members, means to effect engagement of said toothed members upon synchronism of their rotational speeds, an auxiliary normally-open engine throttle valve, and

means connected to said throttle valve and operable upon movement in one direction to .eilect progressive movement of said throttle valve from an open position toward closed position and back to an open position to thereby synchronize said toothed members, said means being operable upon its return movement to likewise eiIect progressive movement of said throttle valve from an open position toward a closed position and back to an open position to permit disengagement of said toothed members.

2. In combination, aninternal combustionen gine, a changespeed gearset therefor including a pair of engageable toothed members, means to permit engagement of said toothed members only upon synchronism of their rotational speeds,

means controllable to urge said members toward of said throttle valve from an open position toward a closed position and back to an open position to thereby synchronize saidtoothed members, said means being operable upon its return movement in the opposite direction to likewise effect progressive movement, of said throttle valve from an open position toward a closed positionl and back to an open position to permit disengagement of said toothed members, and a single control member operable to control both said urging means and said throttle valve operating means.

ROLAND CHILTON. 

